1. Field of the Invention
The present invention relates to an apparatus for controlling the temperature of fat-containing materials, such as flowable chocolate or the like.
In order to impart a specific structure to chocolate materials having the smallest possible and regularly distributed crystals, it is known to control the temperature thereof to bring it into a viscous flowable state and to mix it by means of agitators. For this purpose it is known to carry out the temperature control or tempering in a cylindrical annular chamber between a rotor housing and a rotor rotating therein. The rotor housing is temperature-controlled so that the chocolate is in a viscously flowable state. In this manner, the crystals thus achieve their desired mini-structure. Through the rotation of the rotor the chocolate is caused to be thoroughly mixed, uniform distribution of the miniaturized crystals being achieved thereby.
In this process the chocolate must be prevented from being deposited on the inner wall of the rotor housing. If this were not to be counteracted, the inner wall of the rotor housing would rapidly become coated with a cohesive layer of chocolate. This would prevent the transfer of heat between the rotor housing and the chocolate material exteriorly of the layer adjoining the inner wall of the rotor housing, with the result that the cooling capacity would have to be increased in an attempt to discharge sufficient heat through the layer of adhering chocolate and out of the chocolate material to the outside of the layer, and this would impair the economy of the process. On the other hand, the chocolate of the adhering layer and the other chocolate material would not be admixed, and it is precisely this step which must be afforded according to the object of the process, because uniform distribution of minimum sized crystals must be achieved by the mixing operation. Finally, if the chocolate were to be subjected to too low a temperature for a long period, the crystals in the layer adhering to the inside of the housing would be stimulated into continual growth. The required minicrystals can be obtained only by means of a specific temperature acting over a specific period. An ordinary rotor rotating in a housing would therefore provide uniform distribution of minimum sized crystals in respect of the chocolate situated in the cylindrical annular chamber between the rotor and the housing, but these crystals would not be uniform.
2. Discussion of the Prior Art
In recognition of this drawback it is already known to provide the rotor with scrapers which are resiliently pressed against the inside of the rotor housing and continuously scrape the chocolate from the housing wall while the rotor rotates. These scrapers divide the annular space between the rotor and the housing into individual sections which communicate through constrictions formed in the region of the scrapers. The friction of the metal scrapers on the interior metal does not only free the chocolate from the inside of the housing wall but, additionally, provides a miniaturizing effect which assists the tempering or temperature control process. There is an extensive mechanical miniaturization of the crystals as a result of the friction of the scrapers on the housing wall, in addition to the miniaturizing effect already thermally achieved by the temperature effect.
This method of treating chocolate in every instance requires conveyor means in order to bring the chocolate into the temperature-control apparatus and to remove it therefrom after the treatment.
A temperature-control device in which the chocolate is moved continuously through the housing by means of a screw during the temperature control operation is also presently known. Through this solution, however, it is impossible to prevent a layer from adhering to the inside of the housing. The disadvantages of this layer have been described hereinabove. Although an attempt can be made to maintain the radial clearance between the screw and the housing small and to thus promote the formation of only a thin layer, neither the radial clearance nor the formation of the layer can be completely avoided.